1. Field of the Invention
The present invention relates to a substrate cleaning technology for cleaning substrates such as a semiconductor wafer and a glass substrate (Liquid Crystal Display (LCD) substrate) prior to immersion exposure.
2. Description of the Related Art
In a fabrication process of a semiconductor device or an LCD, photolithography is indispensable in order to form a predetermined photoresist pattern on a substrate. The photolithography includes a series of processes of coating photoresist solution in order to form a resist film on the substrate such as a semiconductor wafer (referred to as a wafer below), exposing the resist film with exposure light through a photomask, and developing the resist film. Such processes are generally carried out in a resist pattern forming system having a coater/developer for forming the resist film and developing the resist film after the exposure and an exposure apparatus connected to the coater/developer.
With further reduction in a circuit pattern and a film thickness, increased resolution of the lithography is greatly demanded. In order to address such demand, so-called immersion exposure is under consideration. In immersion exposure process, a liquid layer is formed on the photoresist film and the exposure is carried out through the liquid layer on the photoresist film. Specifically, the liquid layer is formed between the wafer and a projection lens provided in an exposure apparatus, and the exposure light is illuminated onto the photoresist film through the projection lens and the liquid layer, thereby transferring a predetermined circuit pattern in the photomask onto the photoresist film. More specifically, the projection lens is positioned in a predetermined chip area in order to expose the chip area, and then laterally slid while the liquid layer is kept between the wafer and the projection lens, so that the projection lens is positioned in the adjacent chip area, thereby exposing the adjacent chip area. Such a procedure is repeated to expose all the chip areas in the wafer.